Chapter 14 Simulation and Other Applications

2 What Is Simulation? Simulation A model of a complex system and the experimental manipulation of the model to observe the results Systems that are best suited to being simulated are dynamic, interactive, and complicated Model An abstraction of a real system It is a representation of the objects within the system and the rules that govern the interactions of the objects

3 Constructing Models Continuous simulation –Treats time as continuous –Expresses changes in terms of a set of differential equations that reflect the relationships among the set of characteristics –Meteorological models falls into this category

4 Constructing Models Discrete event simulation Made up of entities, attributes, and events –Entity The representation of some object in the real system that must be explicitly defined –Attribute Some characteristic of a particular entity –Event An interaction between entities

5 Queuing Systems Queuing system A discrete-event model that uses random numbers to represent the arrival and duration of events The system is made up of –servers –queues of objects to be served Please wait!

6 Queuing Systems To construct a queuing model, we must know –The number of events and how they affect the system in order to determine the rules of entity interaction –The number of servers –The distribution of arrival times in order to determine if an entity enters the system –The expected service time in order to determine the duration of an event

7 Meteorological Models Meteorological models Models based on the time-dependent partial differential equations of fluid mechanics and thermodynamics Initial values for the variables are entered from observation, and the equations are solved to define the values of the variables at some later time

8 Meteorological Models

9 Computer models are designed to aid the weathercaster, not replace him or her –The outputs from the computer models are predictions of the values of variables in the future –It is up to the weathercaster to determine what the values mean

10 Meteorological Models Relocatable models Models applied to a moving target Can you think of an example? What is special about weather models?

11 Hurricane Tracking Figure 14.2 Improvements in hurricane models (GFDL) Geophysical and Fluid Dynamics Laboratory

12 Graphics Originally the language of communications for engineers, designers, and architects Computer-aided design (CAD) A system that uses computers with advanced graphics hardware and software to create precision drawings or technical illustrations

13 Graphics Figure 14.3 Geometric modeling techniques

14 Graphics Shape and surface influence an object’s appearance Equations used to describe planes, spheres, and cylinders Real world surfaces are rough, which scatter light differently, requiring texture mapping techniques

15 Graphics Illumination model Simulation of light interaction at one point on an object Shading model (shading) Process of using an illumination model to determine the appearance of an entire object Rendering The process of creating an entire image

16 Modeling Complex Objects Figure 14.5 A natural computer generated landscape

17 Modeling Complex Objects Figure 14.6 Midpoint subdivision for creating fractal terrains

18 Modeling Complex Objects Figure 14.7 Water pouring into a glass

19 Modeling Complex Objects Figure 14.8 Cellular automata-based clouds

20 Modeling Complex Objects Figure 14.9 A campfire

21 Modeling Complex Objects Figure A simulation of cloth showing ending and draping

22 Modeling Complex Objects What is the most difficult object to model?

23 Embedded Systems Embedded systems Computers that are dedicated to perform a narrow range of functions as part of a larger system Empty your pockets or backpacks. How many embedded systems do you have?

24 E-Commerce Electronic commerce The process of buying and selling products and services using the WEB Can you name at least 3 e-commerce sites that you have visited lately? What made e-commerce feasible and easy? What problems does e-commerce face?

25 Computer Security Authentication credentials Information users provide to identify themselves for computer access User knowledge name, password, PIN Smart card card with embedded memory chip used for identification Biometrics human characteristics such as fingerprints, retina or voice patterns

26 Computer Security Malicious Code A computer program that attempts to bypass appropriate authorization and/or perform unauthorized functions Worm stand alone, targets network resources Trojan horse disguised as benevolent resource Virus self-replicating Logic bomb set up to execute at system event

27 Computer Security Security Attacks An attack on the computer system itself Password guessing obvious Phishing trick users into revealing security information Spoofing malicious user masquerades as authorized user Back door unauthorized access to anyone who knows it exists

28 Computer Security Buffer overflow defect that could cause a system to crash and leave the user with heightened privileges Denial-of-service attack that prevents authorized user from accessing the system Man-in-the-middle network communication is intercepted in an attempt to obtain key data Have you ever experienced one of these?